No abstract

Biliary atresia is an inflammatory fibrosclerosing lesion of the bile ducts that leads to biliary cirrhosis and is the most frequent indication for liver transplantation in children. The pathogenesis of biliary atresia is not known; one theory is that of a virus-induced, subsequent autoimmune-mediated injury of bile ducts. The aim of this study was to determine whether autoreactive T cells and autoantibodies specific to bile duct epithelia are present in the rotavirus (RRV)-induced murine model of biliary atresia and whether the T cells are sufficient to result in bile duct inflammation. In vitro analyses showed significant increases in IFN-␥-producing T cells from RRV-diseased mice in response to bile duct epithelial autoantigen. Adoptive transfer of the T cells from RRV-diseased mice into naïve syngeneic SCID recipients resulted in bile duct-specific inflammation. This induction of bile duct pathology occurred in the absence of detectable virus, indicating a definite response to bile duct autoantigens. Furthermore, periductal immunoglobulin deposits and serum antibodies reactive to bile duct epithelial protein were detected in RRV-diseased mice. In conclusion, both cellular and humoral components of autoimmunity exist in murine biliary atresia, and the progressive bile duct injury is due in part to a bile duct epithelia-specific T cell-mediated immune response. The role of cellular and humoral autoimmunity in human biliary atresia and possible interventional strategies therefore should be the focus of future research.

Biliary atresia (BA) is an inflammatory cholangiopathy of infancy. A proposed mechanism regarding the pathogenesis of BA is that of a virus-induced, immune-mediated injury to bile ducts. The rotavirus (RRV)-induced murine model of BA was utilized to determine the hepatic inflammatory response related to ductal obstruction and if the immune response recapitulated human BA. One week after infection, there was a significant increase in liver CD4 + T cells producing IFN-γ and in macrophages producing TNF-α. The intrahepatic pattern of inflammation evolved rapidly from an initial predominant CD4 + Th1 cellular response to a subsequent influx of activated macrophages producing TNF-α and iNOS. This immune response persisted despite viral clearance and was representative of the hepatic immune profile present in human BA. Utilization of the murine model of BA yielded mechanistic data that can provide much needed insight into the role played by different arms of the immune system related to the pathogenesis of human BA.

Biliary atresia (BA) is a progressive, inflammatory cholangiopathy that culminates in fibrosis of extrahepatic and intrahepatic bile ducts. A leading theory on the pathogenesis of BA is that the bile duct damage is initiated by a virus infection, followed by a bile duct-targeted autoimmune response. One mechanism of autoimmunity entails diminished number or function of regulatory T cells (Tregs). The aim of this study was to identify potential virus-specific liver T cells from infants with BA at the time of diagnosis, implicating the virus involved in early bile duct damage. A subaim was to determine if presence of virus infection was associated with quantitative changes in Tregs. Results: Liver T cells from BA and control patients were cultured with antigen presenting cells in the presence of a variety of viral or control proteins. 56% of BA patients had significant increases in IFN-γ-producing liver T cells in response to cytomegalovirus (CMV), compared to minimal BA responses to other viruses or the control group CMV response. In addition, a positive correlation between BA plasma CMV IgM and liver T cell CMV reactivity was identified. Investigation of peripheral blood Tregs revealed significant deficits in Tregs frequencies in BA compared to controls, with marked deficits in those BA patients who were positive for CMV. Conclusions: Liver T cell responses to CMV were identified in the majority of BA patients at diagnosis, suggesting perinatal CMV infection as a plausible initiator of bile duct damage. Deficiency of Tregs in BA implies decreased inhibition of inflammation and autoreactivity, potentially allowing for exaggerated bile duct injury.